Ladder levelling device

ABSTRACT

A ladder safety device includes a carrier structure capable of attachment to a ladder so as to carry the feet of the ladder. The carrier structure incorporates fixedly mounted first interconnect device, ground-engaging feet devices, and linkage arrangement connected to the ground-engaging feet devices and includes a second interconnection which is capable of releasably interconnecting with the first interconnect device to enable verticality of a ladder when the ground-engaging devices engage an inclined surface. Rigidity between the ground-engaging devices and the carrier structure is provided by interconnection of the first and second interconnect devices.

This invention relates to a ladder levelling device.

According to the present invention a ladder levelling device ischaracterised by the combination of a carrier structure capable ofattachment to a ladder and adapted releasably to receive the feet of theladder in a sliding fit at spaced apart stations on the structure, saidstructure incorporating fixedly mounted first interconnect meansextending substantially linearly between said stations, first and secondadjustably mounted ground-engaging means, and articulated linkage meansconnected to the first and second ground-engaging means and includingsecond linearly extending interconnect means for releasablyinterconnecting with said first interconnect means, said secondinterconnect means extending parallel to said first interconnect means,each of said interconnect means comprising interconnect elements capableof connecting the second interconnect means to the first interconnectmeans at a selected one of a plurality of locations along the length ofthe first interconnect means, wherein the linkage means is resilientlybiassed against said interconnection being effected in the absence ofladder weight being applied to said carrier structure, whereby to permitby selective interconnection of the first and second interconnect meansverticality of a ladder when the ground-engaging means are supported byan inclined surface, with rigidity between the ground-engaging means andthe carrier structure provided by said interconnection of the first andsecond interconnect means.

The first and second interconnect means may each take the form of atoothed rack or one may take the form of a rack whilst the other maytake the form of a member having at least one tooth which isinterengageable with the rack. Alternatively, one may take the form of amember defining a series of sockets whilst the other is in the form of amember having at least one spigot. A still further alternative is forone to take the form of a member defining a series of spigots whilst theother is in the form of a member having at least one socket.

Preferably the linkage means includes a stop member which, in theabsence of ladder weight, supports the second interconnect member.

Preferably said first interconnect means and said second interconnectmeans each extend generally horizontally when the device is in use, thefirst interconnect means being substantially at right angles to thelength of the ladder.

Preferably said ground-engaging means comprises a pair of feet memberseach pivotally mounted on the lower portion of the carrier structure.Alternatively the ground-engaging means may comprise a pair of feetmembers each slidably mounted on the carrier structure.

Preferably the carrier structure is of box-like configurationdimensioned to receive the ladder feet in a sliding fit.

Preferably the carrier structure incorporates clamp means for clampingto the ladder. The clamp means may clamp to the ladder feet or to aladder rung or tread.

An embodiment of the present invention will now be described by way ofexample with reference to the accompanying drawing, in which:

FIG. 1 is a front view of a device according to the present invention;

FIG. 2 is a rear pictorial view of the FIG. 1 device; and

FIGS. 3, 4 and 5 schematically illustrate alternative versions of ladderlevelling devices.

As is shown in the drawings a ladder levelling device 10 comprises abox-like carrier structure 11 having a front panel 11a, side panels 11Band a truncated rear panel 11C, the side panels being braced by a bar 12which forms a platform for supporting the feet of a ladder (not shown)in the regions where the bar 12 meets with the side panels 11B, thedepth and spacing of the panels 11B of the structure 11 beingdimensioned to receive the ladder feet in a sliding fit.

As is shown in FIG. 1 the structure 11 has an upper portion to which isaffixed a toothed rack 14 the teeth of which extend horizontally and aredownwardly presented. The lower portion of the structure 11 supportsground-engaging means in the form of a pair of feet members 15A, 15B,each pivotally mounted at 16A, 16B, to enable variable inclination ofthe ground-engaging means with respect to the upper portion of thestructure 11. Toothed linkage means 17 releasably interconnect theground-engaging means with the fixed rack 14, means 17 including atoothed link member 18 with horizontally extending teeth which areupwardly presented and which, in use, engage with the teeth of the fixedrack 14. Member 18 is connected by pivotally mounted links 19A, 19B, tothe respective feet members 15A, 15B, each of the links 19A, 19B, beingresiliently biassed by respective springs 20A, 20B, to hold the linkmember 18 against a stop member 21 secured to the lower portion of thestructure 11 so that there is an absence of engagement between linkmember 18 and rack 14 in the absence of ladder weight being applied tothe structure 11.

The feet members 15A, 15B: may incorporate enlarged ground-engagingportions in order to reduce the applied pressure when the device is inuse.

When the levelling device 10 is in use and weight is applied via theladder to the structure 11 feet members 15A, 15B, in mechanical reactionwith the ground or other supporting structure pivot and cause member 18to move away from stop member 21 into engagement with the fixed rack 14,the tooth-to-tooth interengagement providing rigidity to the device 10.When the ground-engaging means formed by feet members 15A, 15B, aresupported by an inclined surface vertically of the ladder is achieved bylateral movement of member 18 with respect to the fixed rack 14 prior toenmeshing of the teeth, this being achieved automatically by handmanipulation of the ladder axis and intermittent release of the ladderweight from the structure 11 which, in turn, permits intermittentrelease of the enmeshing teeth and lateral movement of member 18 underthe influence of one of the foot members 15A, 15B against the ground.

It will be appreciated that springs 20A, 20B form a resilient biassingmeans but that this need not be in the form of springs as illustrated.Furthermore although the pitch of the teeth on link member 18 requiresto match that of the teeth on rack 14 to permit enmeshing the shape ofthe teeth on member 18 need not be exactly the same on components 14 and18. For example, the teeth on rack 14 may be provided with offset apicesto reduce the possiblity of apex to apex jamming which although existingwith a small probability level is desirably minimised in the interest ofsafety.

In another modification the tooth racks are replaced with membersdefining pin and socket interconnections and the protruding ends of thepins may be coned or domed to facilitate entry into the sockets. Thefeet members may incorporate individual extension pieces providingextension in either or both of the vertical and horizontal directions,these extension pieces being connected to the feet members by clamps.The stop member 21 may be replaced with a pair of spaced roller elementswhich, together function as a stop member for the moving member 18.Springs 20A, 20B may act indirectly on the linkage means 17, forexample, by biassing roller elements against the upper surface of themember 18.

In the version of the device 10' illustrated in FIG. 3 the structure 11with its front panel 11A' is provided with slidably mounted feet members15A', 15B', by virtue of mountings 16A', 16B', formed by lateralextension of fixed member 14' at the top of the structure and by amember 23 at the bottom of the structure. Links 19A', 19B', interconnectfeet members 15A', 15B', with movable member 18' which is supported byrollers 21'. The mating surfaces of members 18', 14' in this instanceare friction surfaces and rigidity of interconnection is assured by ahand operated clamp 22 which is mounted on the structure 11. Operationof device 10' is essentially the same as that of device 10.

In the FIG. 4 form of the device feet members 15A, 15B are mounted bypin and slot connections 16A, 16B on the structure 11 and areinterconnected by bar member 18 by pin joints 28A, 28B, member 18 beingcapable of sliding laterally with respect to a guide member 29 fixedlysecured to the structure 11. Interengagement between toothed members 14and 18 occurs when the device is in use by virtue of the pin and slotconnection 16A, 16B the slots of which are formed in the carrier 11 andextend vertically, which is orthogonally with respect to member 18.

In the FIG. 5 form of the device the feet members 15A, 15B are unitedand mounted on the carrier 11 by a single pin and slot connection 30,the pin being carried by the carrier 11. The members 15A, 15B are alsopivotally connected to bar member 18 which is capable of slidinglaterally with respect to stud members 14A, 14B secured to the carrier.Toothed members 14C, 14D interengage with toothed parts of member 18 toprovide security.

The levelling device which has been described also finds use with aladder in the form of a stepladder in which case it can be used eitheron the front feet formed by a tread-carrying styles or on the rear feet.

I claim:
 1. A ladder levelling device is characterised by thecombination of a carrier structure capable of attachment to a ladder andadapted releasably to receive the feet of the ladder in a sliding fit atspaced apart stations on the structure, said structure incorporatingfixedly mounted first interconnect means extending substantiallylinearly between said stations, first and second adjustably mountedground-engaging means and articulated linkage means connected to thefirst and second ground-engaging means and including second linearlyextending interconnect means for releasably interconnecting with saidfirst interconnect means, said second interconnect means extendingparallel to said first interconnect means, each of said interconnectmeans comprising interconnect elements capable of connecting the secondinterconnect means to the first interconnect means at a selected one ofa plurality of locations along the length of the first interconnectmeans, wherein the linkage means is resiliently biassed against saidinterconnection being effected in the absence of ladder weight beingapplied to said carrier structure whereby to permit by selectiveinterconnection of the first and second interconnect means verticalityof a ladder when the ground-engaging means are supported by an inclinedsurface, with rigidity between the ground-engaging means and the carrierstructure provided by said interconnection of the first and secondinterconnect means.
 2. A ladder levelling device as claimed in claim 1,characterised in that the first and second interconnect means each takethe form of a toothed rack.
 3. A ladder levelling device as claimed inclaim 1, characterised in that one of said interconnect means defines aseries of sockets and the other defines at least one spigot which isinterengageable with the sockets.
 4. A ladder levelling device asclaimed in claims 1, 2 or 3, characterised in that said ground-engagingmeans are pivotally mounted on the lower portion of the carrierstructure.
 5. A ladder levelling device as claimed in claims 1, 2 or 3,characterised in that the ground-engaging means are slidably mounted onthe carrier structure.
 6. A ladder levelling device as claimed in claim1, characterised in that the carrier structure incorporates clamp meansfor clamping to the ladder.